Parting 304 steel.

[lellasone]

Hi All,

I am in the process of making a hammer (of sorts) and was given a piece of 304 steel, which I have never used before. The "filing to shape" portion of the experiment wen't well, if slowly, but when it came time to cut off the hammer head from my round-stock the stock more or less ate my HSS parting tool. I was with cutting fluid and no coolant (not working) at 68sfpm.

Once the student shop Johnson saw is working again I will probably just use that, but in the mean time I was wondering if there is anything I should watch out for to make similar operations more successful in the future.

Thanks and all the best,
Jake

 

[mikey]

If you're talking about 304 stainless steel then I'm not surprised it dulled you HSS tool. HSS will cut 304 but you need to keep it constantly cutting or the surface will work harden and that will stop the cutting action. At this point, you have some options: use a carbide parting blade or hacksaw it off and face or if you're up to it, sharpen your HSS blade and introduce it to the work and while firmly feeding into it, turn the chuck by hand. You may be able to get under that hardened surface and the tool will cut again. If this works, turn the lathe on and feed with enough pressure to keep the tool cutting. Use lots of cutting fluid and you should be okay.

 

[Silverbullet]

Some 304 and 316 stainless , will harden very quickly and it eats high speed tool bits . You should be ok with carbide. We used stainless alot on government contracts for missle parts and rockets we built. Back then we were hush hush but now the shops changed hands and I bet contracts are long ago filled. We made the hook mounts out of 316 , hand polished to pass inspection. My boss was very happy with our shift for completeing the jobs handed to us with only hours to get them done. At the time I introduced insert milling cutters to them , after ruining about ten double endmills per shift facing the clamping pieces in a jig on a bridgeport. It ment saving hours wasted doing mill changes and reset ups. Just rotate the carbides and they lasted five times longer the high speed cutters. Really tuff steel to work with without carbide. I wouldnt be surprised if the saw blade dont skate off too. If you use abrasive cut off try using some coolant , it will make filing and polishing better.

 

[lellasone]

Mikey - I hadn't considered that work hardening would be an issue, but in retrospect that makes a lot of sense. I ended up using a vertical bandsaw running very slowly and that has worked out well enough. If I get the chance at some point I will play around with trying to feed a parting tool under a hardened surface the way you suggested. (Also tried using a hacksaw, worked but way slow...)

Silverbullet - Many thanks for sharing for the story, it was a great read to start the day.

 

[Wreck™Wreck]

Parting 101.
Square tool with an indicator.
Set height on center, with other tools I set the height from the ways with a ruler, on this machine 8 1/16", for parting tools place a piece of scrap in the chuck and adjust upwards until the nub disappears.
Part as close to the chuck as possible.
Select feed and spindle speed.

On this job, 1" round 304 stainless I used the parting tool as a work stop, turned to a shoulder with chamfers and parted off 1" long to center, 36 parts.



There is nothing special about this lathe, it is a 20 year old Romi 15 X 36 engine lathe with a Bridgebort control, Aloris QCTP and fixed spindle speeds, the parting tool plunges to .95" diameter then retracts and then puts a .025" chamfer on the back then parts to center, 1500 RPM's, .012 feed roughing and .004 for finishing when OD turning, 750 RPM's at .001 Inch per Revolution for parting and catching them by hand. 57 seconds per part.